I. Field of the Invention
The present invention relates generally to the field of crank-throw adjustment mechanisms in which length of crank throw of a pedal crank is adjustable on mechanisms such as leg exercisers, pedal boats and bicycles.
II. Description of the Prior Art
Previous adjusters of length of crank throw of pedal cranks for bicycles and other mechanisms operated similarly have employed a variety of bolt-setting and sliding mechanisms. None have employed length adjustment of a triangular base that is common to two opposed triangles in the manner taught by this invention.
Typical of length adjustment with bolt settings are U.S. Pat. Nos. 393,837, 363,522, 4,850,245 and 4,915,374. Length adjustment with slide mechanisms have included U.S. Pat. Nos. 4,648,287, 625,986 and 359,609. Although adjustment of length of pedal-crank throw is an old art in which U.S. patents were granted over 100 years ago, neither the mechanism nor the geometrical principle employed in this invention has been employed for adjustment of length of crank throw for pedal-opearable machines such as exercisers, bicycles, pedal boats and other pedal-operable machines.
The principle of varying length of a common base of opposed triangles to vary distance between their opposite angles is known in mathematical concept and has been used in some mechanisms. Its use in mechanisms, however, has been limited to car jacks and other positional devices that employ the principle differently. Employing the principle for length adjustment of a pedal-crank throw requires new and different features for achieving rotation than for car jacks and other non-rotational or variously positional devices. Long use of pedal machines when this length-adjustment mechanism in different forms has been known is indicative of novelty that comprises invention such as this crank-throw-adjustment mechanism.
Previous leg exercisers and arm exercisers employing the pedal principle have not been conveniently and easily adjustable in length of crank throw. Adjustability of throw length, however, is highly advantageous to exercise movement for exerciser machines that employ pedal action. Exercise of legs is often impaired by injuries that also make adjustment of exercise machines difficult. Long and short movement of legs in a pedaling action exercises different muscles that injured people often need to exercise separately and that uninjured people often choose to develop separately. But when throw length of a pedal cranks is fixed or is inconvenient to adjust, it is discouraging and time-consuming for uninjured people and often impossible for injured people. The healthiest of exercisers will want to vary the length of throw of a pedal exerciser quickly and easily as they choose each time they exercise or in accordance with an exercise objective. People with different heights and with different lengths of legs need different lengths of pedal-crank throws for similar purposes. This invention helps all alike. It provides convenient, fast, easy and inexpensive length adjustment for pedal-crank throws. Further, it provides different throw length for each leg selectively for those who require different exercise levels for each of their legs.
Bicyclists and pedal-boaters now are limited to a fixed manufactured length of throw for their bicycles and boats regardless of their physical conditions, size or desires. No previous length adjuster for pedal throws has been sufficiently meritorious to be in demand and to be produced on a wide scale for pedal-operated machines.